The present invention relates to a method and an apparatus for the electroerosive working of workpieces and, more particularly, the generation of the machining pulses.
Spark-erosive working methods, particularly spark-erosive cutting methods, are largely based on empirical findings and hypotheses, because there has hitherto been no conclusive physical description of the discharge processes in the work gap. Thus, in the case of cutting processes using a wire or strip electrode, apart from the effects of gravity, a problem is also caused by vibrations formed as a result of electromagnetic, electrostatic, as well as mechanical or hydraulic effects. In view of such vibrations, and particularly in the case of finishing working conditions which requires very short discharges in the microsecond range and frequencies in the range of approximately 100 to approximately 500 kHz, particularly high demands are made on the generators used. Despite the short discharge time, such generators must supply currents of approximately 200 ampere. The time control of the discharge process has hitherto essentially taken place by the controlled switching on or off of the generator.
With the goal of minimizing disturbances of the erosion process, known generators, as for example those described in German Pat. Nos. 2,908,696 or 2,909,073, provide for the interruption of the discharge process as soon as process abnormalities occur, or when electrode wear exceeds a limit value. In controlling the energy distribution of a discharge, it is known from Swiss Pat. No. 495,812 for example to obtain shaped pulses by the additive timeshifted superimposing of pulses from individual working circuits. However, such generators are only suitable for generating relatively long pulses.